The proposed conference is the thirteenth in a series of Gordon Research Conferences that originated in 1966 with a conference on cardiac muscle. The major focus of the 1981 conference will be the molecular basis and regulation of the contractile process. The work to be presented will deal with mammalian skeletal, cardiac and smooth muscle as well as insect muscle. In the past three years signficant progress has been made in understanding the interaction of the major contractile proteins, actin, myosin and tropomyosin, using low-angle X-ray diffraction, stopped-flow kinetics, chemical probes and active site labeling. Major advances have also been made recently in the amino acid sequencing of myosin and tropomyosin, the characterization of cardiac and skeletal muscle isoenzymes of myosin and in our understanding of how skeletal, cardiac and smooth muscle contractile proteins are regulated. The regulation of smooth muscle is of particular interest since it appears to have the same molecular basis as a major regulatory system present in many non-muscle eukaryotic cells. It will be the purpose of this conference to sumarize the major areas of progress during the past 3-5 years, and to point the way to those areas which should prove productive for research in the immediate future. The conference will include formal presentations, including a brief summary of the progress made in the major areas. There will be only a limited numbrer of formal presentations with emphasis being placed on discussion and informal interchanges. In order to expand the number of participants without curtailing discussion periods, ample use will be made of poster presentations and a specific session will be devoted to a discussion of the material presented on the posters. This conference is of particular importance in bringing together scientists representing a variety of disciplines who are actively involved in research on muscle contraction. In allowing scientists of diverse backgrounds to focus on the molecular mechanism and regulation of muscle contraction for a week, this conference should help to open new areas of research as well as provide a meaningful reexamination of previously accepted ideas.